Long noncoding RNAs (lncRNAs) are noncoding long (>100 bases) single- stranded RNAs that have burst onto the scene as major regulators of gene expression. MicroRNAs, are about 22 base long single-stranded RNAs that came to the fore about a decade back and this laboratory has been among the pioneers that demonstrated the roles of several microRNAs in the differentiation of skeletal muscle myoblasts to myotubes. We now propose to use our expertise in the role of RNAs in muscle differentiation to determine the mechanism by which one particular muscle- differentiation-induced (MDI) lncRNA, MUNC, regulates gene expression and promotes muscle differentiation. Aim 1 will test the hypothesis that MUNC is essential for muscle differentiation because of its role in either regulating the binding or the expression of critical myogenic transcription factors as a constituent of novel protein complexes involved in gene regulation. Aim 2 will carry out structure function studies on mouse and human MUNC to test the hypothesis that evolutionarily conserved domains exist in this lncRNA that are critical for its mechanism of action. Aim 3 will identify new protein and DNA partners of MUNC to identify functions of MUNC independent of Myogenic transcription factors. This Aim will also identify additional lncRNAs that are induced during muscle differentiation and integrate their role in differentiation with that of MUNC and MyoD. This is an exciting project that involves the collaboration of a molecular biologist with a skeletal muscle physiologist. It wil use new experimental reagents such as lncRNAs and state-of-the-art approaches like ChIRP. LC-MS-MS, SILAC and ChiRP-seq to discover the mechanism of action of one lncRNA in control of cell-type specificity. Since our preliminary results identify tens of novel lncRNAs induced during differentiation, at least some of which already implicated in differentiation, success of this project will launch a prolonged investigation of several lncRNAs in this very important paradigm of differentiation.